Some power equipment can consume a significant volume of gasoline and/or other fuels during operations. For example, in order to propel some power equipment, an internal combustion engine can require fuel to provide power to a drive train that, in turn, can provide motive force to the equipment. Gasoline and other fuel costs can be substantial for some pieces of power equipment operated by businesses and consumers. Some manufacturers now provide electric machines, such as permanent magnet motors, within the drive trains, to supplement or eliminate the constant need for internal combustion engine activity. Unfortunately, such electric machines are typically expensive and require expensive batteries for useful operations. In addition, some of these electric machines can lock or limit the power of a conventional internal combustion engine-powered equipment.